In deep mines and in certain other areas where enormous head of water is available to power equipment there is a need for rock drills and other devices which can be powered by such hydropower installations. Hydraulic rock drills which operate on a 5/95 oil and water emulsion are now commercial. However, they will not effectively work on pure water. There exists therefore a need for mine worthy devices which can transform the potential energy of a hydropower installation into a pressure fluid which can power commercially available emulsion driven rock drills. Intensifiers, typically oil to water, are common pieces of machinery. The difficulty of the hydropower requirement is that unlike conventional fluid transformers (which use oil to lubricate complex control valves) the valving must operate in corrosive nonlubricating water. In order to insure successful operation of a transformer used in a mine the device must be simple, reliable and durable. Due to the complexities of the existing art it is felt that the device according to the present invention will provide an advantage to the industry.